1. Field of the Invention
The present invention relates to a parking apparatus for a continuously variable transmission and, more specifically to, a parking apparatus capable of operating a parking mechanism and manual valve operating mechanism with a single driving shaft.
2. Prior Art
In recent years, increasing number of vehicles are equipped with so-called continuously variable transmission in which the transmission speed ratio is changed automatically by means of changing the pulley diameter according to operating conditions. Generally, a vehicle incorporating the continuously variable transmission has a select lever in the passenger compartment so as to obtain an automatic speed change according to range positions selected by the select lever. The range positions include a forward range (D), a reverse range (R), a neutral range (N) and a parking range (P). When the select lever is positioned at the parking range, the continuously variable transmission is constituted in such a manner that its secondary pulley is locked. Specifically, when the select lever is operated, a manual shaft is rotated through a cable interconnecting between the transmission and select lever. A rod and linkage mechanism connected with the manual shaft operates a parking mechanism so as to lockup rotation of the secondary pulley.
The cable interconnecting between the continuously variable transmission and select lever, in case of where the continuously variable transmission is mounted transversely, is connected with the top or front surface of the transmission but not with the side surface thereof because the side face is occupied with a differential gear device and a constant-velocity universal joint. Further, it is desirable from the view point of the reduction of friction and the improvement of endurance that the cable is arranged among components such that the bending radius is as large as possible. To realize this, the manual shaft is preferably disposed at a remote place from the cable connecting point on the select lever. Further, similarly it is preferable that the rod and linkage mechanism for operating the parking mechanism is disposed at a remote position from the select lever.
For example, in the parking mechanism disclosed in Japanese Patent Application Laid-open No. Toku-Kai-Hei 5-322043, a rotating rod for the parking mechanism is disposed on the front upper surface of the transmission. In this case, a connecting rod connected with the rotating rod is provided in the orthogonal direction of the engine crank shaft in a dead space under the engine output shaft. Further, the connecting rod is engaged at other end thereof with a lever and the lever operates a parking pawl so as to lock one of parking gears with its pawl section.
Further, Examined Japanese Patent Application No. Toku-Kou-Hei 3-30540 discloses a construction in which a parking lock shaft is disposed at the front of the transmission. Also in this disclosure, the parking lock shaft is disposed at a remote position from the select lever.
On the other hand, the select lever is interlocked with a manual valve for changing over hydraulic pressure of a clutch and brake of a forward and reverse changeover apparatus. Studying the change-over mechanism of the manual valve from the view point of the interior structure of the transmission, in case where the manual valve is accommodated in an oil pan disposed under the transmission together with miscellaneous control valves, it is necessary to arrange a shaft for operating the manual valve in a space close to the manual valve and not interfering with other power drive shafts. Generally, the transmission thus constituted has a narrow range of choice in incorporating the shaft. Especially, since a transversely mounted continuously variable transmission has four drive shafts (primary shaft, secondary shaft, drive pinion and differential gear), this kind transmission has much more difficulty than a conventional planetary type automatic transmission.
To overcome this difficulty, Registered Japanese Utility Model Application No. 2547900 proposes a technique in which the manual shaft is divided into two shafts provided in parallel with each other. In this case, the manual shafts can be accommodated in a limited space between drive shafts. Further, in another disclosure, there is a technique in which the manual valve is disposed on the upper surface of the transmission separately from the control valve body. According to this technique, the manual shaft does not penetrate through the transmission case up to the oil pan.
In case where the manual shaft can not be disposed in a position appropriate for connecting the cable due to the problem of the interior structure of the transmission, there is a technique wherein the cable is connected to the manual shaft through a parallel link provided on the transmission. However, this method has such problems as a malfunction of the link mechanism, a low positioning accuracy in operating the manual valve and others.
Since the continuously variable transmission can not accommodate a parking mechanism around the primary shaft because of the structural reason of the transmission, the parking gear is mounted on the secondary pulley. In this case, as a distance between the parking gear and manual shaft is smaller, designing of the parking mechanism becomes easy. Accordingly, it is desirable to reduce that distance as far as possible. For example, Japanese Patent Application Laid-open No. Toku-Kai-Shou 58-207571 proposes a parking lock mechanism in which a cam guided by a sleeve is formed at the end of a rod slidably operative by the manual shaft and the cam pushes up a pawl in the direction of locking the parking gear. If the distance between the parking gear and manual shaft is unduly large, the following mechanical problem is caused.
That is, if the distance between both is too large, the lever provided between the parking gear and manual shaft is elongated and the offset amount of the rod becomes increases. This brings about a large space for swinging of the lever and a lack in the parking force. Further, a parking mechanism in which the rod is arranged in the direction of the secondary shaft and the pawl is operated like a seesaw according to rotation of the manual shaft, can be considered but this type of mechanism has a problem in that the width of the transmission increases due to a space for the reciprocating motion of the rod, this resulting in an increase of the size of the overall transmission.
That is, although thus constituted parking apparatus and manual valve changeover apparatus are interlockingly operated by one select lever, these apparatuses are not constituted in such a manner that they are driven by a single driving shaft. That is, the respective mechanisms for finally actuating these apparatuses are constituted independently from each other, this resulting in an increase of the number of components and difficulty in assembling the apparatuses.
The parking mechanism disclosed in Toku-Kai-Hei 5-322043 utilizes a complicated mechanism comprising connecting rods and levers. Additionally, since this continuously variable transmission has a four-shafts construction, it is very difficult to incorporate the parking mechanism into the transmission.
Further, since the construction disclosed in Toku-Kou-Hei 3-30540 has an output shaft below the crank shaft of the engine, normally the secondary pulley is arranged in such a state as dipping in lubrication oil and as a result, agitation loss of the pulley increases. To avoid this, it is considered that the secondary pulley is arranged at a position rotated counterclockwise 90 degrees but this construction has a defect that a frontal clash space on an impact is occupied by the control valve.